This article is from the Car Audio FAQ, by Ian D. Bjorhovde (firstname.lastname@example.org) with numerous contributions by others.
It is getting difficult to find pullout CD players any more, since
detachable faceplates are much more convenient to carry around.
However, there is the obvious trade off - it is still possible to steal
the chassis for the detachable face unit, when that is not possible
with a pullout. Although some companies will advertise that it is very
difficult to get replacement faces without the original receipt,
thieves can still get the faceplates.
Some companies, such as Eclipse, are starting to offer alternative
methods for preventing theft. Some Eclipse decks now offer ESN
(Eclipse Security Network), where the owner chooses a "key" CD that
must be inserted to "revive" the deck should it lose power. The entire
deck stays in the dash, with nothing to carry around; this expands on
the trend towards convenience while offering the owner peace of mind.